For certain uses, in particular for writing, printing and more particularly photo-engraving, non-rough papers are desired which have a good smoothness optionally combined with a good gloss. Of course, these specific properties must not be acquired to the detriment of other qualities of the paper such as mechanical resistance in the dry or wet state allowing high production rates, good absorption of inks without running, or smudging, or penetration, opacity, whiteness. Giving papers gloss by calendering is well known, combined with a judicious choice of pigments. As for smoothness, it is at present obtained by a difficult compromise between costs and industrial possibilities of the paper maker as a function of the state of the support surface and its formation, the content and nature of the solid matter of the coating, the coating device used, the weight of the deposit and calendering conditions.
As a result, starting with a given support, the paper maker desiring to obtain a paper which has a good smoothness is confronted with a problem which he attempts to solve by a compromise which necessitates numerous costly tests.